Hershey and Chase used the 35S isotope to label proteins. How does this isotope differ from the 32S isotope found in greatest natural abundance, and why did they choose 35S instead of 32S?

35S has more protons than 32S; Hershey and Chase used it because it has a greater mass.
35S has fewer protons than 32S; Hershey and Chase used it because it is radioactive and can be easily traced.
35S has more neutrons than 32S; Hershey and Chase used it because it is radioactive and can be easily traced.
35S has fewer neutrons than 32S; Hershey and Chase used it because it has a smaller mass.